The present invention relates to a cab for earth-moving machines.
Hereafter, reference shall be made in particular to earth-moving machines of the category known in the art with the name of skid steer loader, whereto the subject invention is preferably destined, although it is applicable in general to all categories of earth-moving machines.
Earth-moving machines are composed of a frame mounted on four wheels, of at least an articulated arm fastened to the frame and bearing a work tool, and of a cab for housing an operator, mounted on the frame. Alternatively, the frame can be equipped with tracks instead of wheels.
Earth-moving machines further comprise a motorized driving system and an arm actuation system. Each machine is also provided with an electrical system.
Typically, the machine is activated by an operator housed in the cab, who acts on two control levers, or other equivalent organs, positioned one to the right and the other to the left of the operator, and connected one to the driving system and the other to the arm actuation system.
The driving system and the arm actuation system are constituted by two hydraulic servo control loops, each comprising at least a pump driven by the engine and a plurality of conduits and valves; each loop is connected between a control lever and the related activated organ.
In accordance with the prior art, the cabs comprise a support structure in which is defined a compartment provided with a seat for the operator.
Other cabs are fitted with doors and/or windows mounted to close the support structure, in order to isolate the operator from the external environment.
In the lower portion of the structure are also provided openings able to allow the operator to move the control levers mounted on the frame.
These cabs are typically mounted in correspondence with the front portion of the frame, where the control levers are installed, so that the levers themselves are in the correct position.
The cab can be mounted on the frame or rigidly or, as taught for instance by U.S. Pat. Nos. 5,520,500, 5,551,826 and 4,409,672, by means of a pivoting joint which allows to tilt the cab either in the forward or backward direction.
In the case of pivotal mounting, locking points must also be provided to prevent the possibility that the cab may be tilted when it is in operative condition.
In the traditional constructive form, all operative organs of the machine are mounted directly on the frame.
These operative organs include the control organs, the articulated arm bearing the working tool, the engine and the hydraulic and electrical systems that connect the control organs to the engine and to the articulated arm.
In traditional solutions, therefore, no part of the operative organs extends into the cab, as the latter is mounted on the frame in correspondence with the position in which the control organs are located.
U.S. Pat. Nos. 5,520,500 and 5,551,826 instead provide a different solution from the traditional one, in that the articulated arm is fastened not to the frame, but to the side walls of the cab which must therefore be load bearing and suitably dimensioned.
This solution consequently requires part of the hydraulic circuit for the servo control of the arm to extend also into the cab, since the hydraulic circuit has to connect the arm with the engine and with the related control lever, both mounted on the frame.
To conciliate this aspect with the tilting of the cab, U.S. Pat. No. 5,551,826 provides for the hydraulic and electrical connections, extending between the frame and the cab, to have a suitable length in order not to interfere with the lifting operations of the cab itself.
Also known are earth-moving machines wherein vibration-damping elements are interposed between the cabs and the frame whereon the cabs are mounted (see for instance U.S. Pat. Nos. 5,551,826 and 4,150,474, in which rubber pads are used).
The prior art described above, however, presents a series of drawbacks.
A first drawback is represented by the noise created by the engine and by the hydraulic systems.
Although cabs can be provided with doors and/or windows for better isolating the operator from exterior noise, the reduction of the noise thereby obtained fails to reach a satisfactory level.
This is due to the fact that the bottom of the cab is provided with openings to allow the operator to access the control levers and hence the cab compartment is not fully isolated from the underlying machine.
A second problem is represented by dust, which is a considerable source of annoyance for the operator and which, like noise, penetrates into the cabs through the openings that the cabs present in their bottom in correspondence with the control levers.
A further problem is represented by the vibrations of the machines which are transmitted to the operator.
These vibrations reach considerable intensities and involve the whole machine, cab included, thereby constituting a considerable source of annoyance for the operator.
Not even the interposition of the vibration-damping elements between the cabs and the frames of the machines whereon the cabs are mounted has fully solved this problems.
The control levers, which are fastened directly to the frame, are affected by all vibrations of the machine and transmit them to the operator.
Cabs constructed according to the teachings of U.S. Pat. Nos. 5,520,500 and 5,551,826 are also affected by a further drawbacks relating to the mounting of the cabs on the earth-moving machines during their production.
The construction of the earth-moving machines is effected in an assembly line, and the different parts of the machine are assembled to the frame in the different phases of the assembly line.
Some of these parts, however, in turn comprise multiple pieces and are thus assembled previously elsewhere.
In particular, the cab comprising lateral walls, roof, bottom portion and seat, is first mounted on its own and then positioned and fastened on the frame in correspondence with the control levers.
For earth-moving machines in accordance with U.S. Pat. Nos. 5,520,500 and 5,551,826, the method for assembling the machines is particularly complicated. The arm and the cab cannot be assembled on their own independently of each other and then be mounted on the frame, since the arm must be mounted on the walls of the cab.
In this situation the technical task constituting the basis for the present invention is to obtain a cab for earth-moving machines that overcomes the aforementioned drawbacks.
Another technical task of the present invention is to obtain a cab for earth-moving machines which provides a good level of reduction in noise, dust and vibration inside the cab during operation.
A further technical task of the present invention is to obtain a cab for earth-moving machines that allows a relatively simple and quick mounting.
The specified technical task and the indicated aims are substantially achieved by a cab for earth-moving machines, as described in the accompanying claims.